In my first column on climate change I discussed what responsibilities it might impose on us as Christians. The latest assessment by the Intergovernmental Panel on Climate Change (IPCC), from 2007, claimed that there was a 90 per cent probability that human activity was the main agent. Given the complexity of the factors there is room to question aspects of this assessment but I think it to be prudent to take the most comprehensive and broadly accepted evidence. I am not qualified to judge between the experts.

The first, and rather dramatic, clue is a graph which shows the growth in the greenhouse gases over the last 10,000 years. (Historical measurements are made through the analysis of ice cores.) It shows a nearly horizontal line until about 200 years ago, coinciding with the Industrial Revolution, which led to a sustained, sharp vertical upturn. Carbon dioxide, which is the major element, shows an increase of 35 per cent over pre-industrial levels; it is growing at its fastest recorded rate. Methane and nitrous oxide have also increased. Halocarbons, resulting from refrigerators and spray propellants, are a man-made new arrival. Our contribution to this is confirmed by the analyses which show that the major source is the burning of fossil fuels, and that the hotspots are located over the areas of high industrialisation.

There are, of course, factors which alleviate the situation: some result from human activity and some from natural conditions. Aerosols, which are airborne particles from sources such as dust storms, forest fire and volcanoes, help in reflecting sunlight back to source, although the process is not fully understood. Solar energy has made a contribution to warming but the effect is small at around a 10th of the whole. Land management has good and bad effects. Measurements taken in 2005 show that the contribution of human activities to climate change outweigh the other factors by a large margin.

Naturally we should expect to see changes caused by these factors: 11 out the last 12 years up to 2006 have been the warmest since 1850, when good records began. The upwards trend in global temperatures measured over the 20th century is accelerating, and the majority of the increase has occurred over the last 50 years. We now experience fewer frosty days and more warm days and nights. This is further confirmed by tree-ring data: the last warm period, around the end of the first millennium, was some degrees cooler than recent average temperatures.

Spring snow cover, which can have a marked effect on water conservation, had decreased in northern latitudes. The sea absorbs much of the additional heat, leading to natural expansion and rising levels. There have been marked reductions in permafrost and the melting of sea ice in Greenland and the Antarctic. Currently, there is insufficient data to judge whether the rate of rise is accelerating. Again, the graphs covering the last 100 years show a steady, threatening trend.

Water vapour in the atmosphere is largely controlled by temperature, and so this has been increasing. Various areas across the world have become wetter, while others have become drier. Disaster has often been the result.

Forecasting the future is a different problem. The principal method is the use of complex models which attempt to take account of perceived relevant values and their interplay. Educated assumptions often have to be inserted, and necessarily the room for error increases with the length of the period predicted. However, many different scientists applying their own models independently give a useful, if not infallible check. Indeed, the predictions made in the previous IPCC assessment in 2001 needed considerable updating in 2007. Some leading climatologists have recently argued that cyclical changes in atmosphere and ocean currents will actually cool the earth over the next 20 years; this may mask the underlying trend.

Many of the future outcomes are unavoidable because we have yet to undergo the full results of past atmospheric changes. Over the next 20 years various scenarios show that an increase similar to our recent experience will continue. Beyond that, the most likely scenarios suggest increasingly higher temperatures by the end of the century (compared to year 2000), in the order of 2°to 4° C, but could be half as much again. It was estimated that sea levels would rise by 30 to 40 centimetres. And accelerated loss of ice from Greenland and the Antarctic would increase this by up to 20 centimetres. Some more recent studies, which look closely at the possible effects of melting ice, suggest an overall sea level rise of a metre and over. A recent report by the Met Office suggests that these changes could occur within 50 years from now. But many factors, and their interaction, within these projections are not yet well understood, and doubtless they will become more accurate as these aspects are more closely studied.

Naturally, different regions of the earth will be affected in different ways and different levels of severity. In a future column on climate change I will look at how different regions of the world may be affected.

How long will the effects of climate change last? We are certainly talking hundreds of years. Hold on to your seat belts for a long and bumpy ride.

Readers who are familiar with the IPCC assessment, will be aware of the sparseness of my description. But I think it better for us to grasp the overall picture which the assessment paints than to get lost in detail. Many interesting and knowledgeable comments have been made to Climate Change – 1. I hope you will continue your critique and suggestions with this second instalment.

12 Responses to Climate Change – 2

The weather is a very awkward thing. It is a completely deterministic system, but unfortunately for us it is also non-linear (or ‘chaotic’), and has lots of unknown (and, in practical terms, unknowable) variables.
One of the few things that can be known with any degree of certainty is that, if the amounts of water vapour, carbon dioxide, methane, nitrous oxide, halocarbons and tropospheric (as opposed to stratospheric) ozone in the atmosphere are increased, then the mean surface temperature of the Earth will rise.
Human beings are currently putting 50 billion tonnes of CO2 into the atmosphere every year. That’s 7.36 tonnes for every man, woman and child on the planet. I do not want to keep repeating myself, but atmospheric CO2 levels have not been as high as they are now for the last 15-20 million years (see: http://www.sciencedaily.com/releases/2009/10/091008152242.htm).
This was during the Miocene Period, when temperatures were 5-10°F higher than they are now, there was no permanent sea ice cap in the Arctic, very little ice on Antarctica and Greenland, and global sea levels were 75-120 ft higher than they are today.
Even if agreement is reached at Copenhagen in December, which is looking increasingly unlikely, atmospheric CO2 concentrations will reach 400 ppmv (parts per million by volume) in a decade, unless something drastic is done to prevent it.
We simply cannot afford an increase in the annual global mean surface temperature of 4°C (= 39.2°F). The impact of such a rise will be devastating, as the Met Office’s Climate Impacts Map demonstrates. (See: http://www.actoncopenhagen.decc.gov.uk/content/en/embeds/flash/4-degrees-large-map-final.)
Climate change scepticism is a luxury we can also no longer afford.

A rise of 4°C = a rise of 7.2°F (which, coincidentally, is more or less how much warmer it is here today than the average for the time of year).

It seems well established that CO2 levels are coupled with atmospheric temperatures. Is it absolutely clear that this is cause and effect? It has been claimed that past temperature rises preceded the CO2 rises – is that wrong?

I would prefer to say that the Climate Map ‘claims’ that a rise of 4°C will be devastating. The claim may be correct (let’s hope it’s never put to the test), but ‘demonstrates’ puts it too high.

The assertion that we cannot afford scepticism needs to be weighed against the cost of the alternative – faith – which is also very substantial.

I remain of the view that the majority of experts is probably right about most of the science, so something should be done. What, when and by whom are not solely scientific questions.

To convert Celsius to Fahrenheit, so says the ‘Chambers Book of Facts’, multiply by 9, divide by 5, and add 32. 4 x 9 ÷ 5 = 7.2, which is, of course, the answer Tim gives – the correct one.
Tim will have to forgive me (at least, I hope he will forgive me) for being an ‘Aspie’ – someone who suffers from Asperger’s Syndrome. When told to do a thing, I am a bit like a computer -I do that thing precisely as instructed. In spite of all my scientific knowledge, and my (alleged) IQ of 150, it never occurred to me not to add the 32. What do you do with me? What do _I_ do with me?
Having made such a stupid and shaming mistake, I feel like going away and burying myself somewhere, and completely disqualified from even attempting to answer Tim’s point.
However, I would point out to Tim that a good many things are a matter of faith. It is a matter of faith that the Sun will rise tomorrow morning; it is a matter of faith that we will still be alive tomorrow morning to see it rise (we might not be – and the older we are, the less certain that is).
He is right to say that the cost will be substantial – but, if the vast majority of scientists are right, the cost of _not_ acting will be even more substantial.
As for his point about temperature rises preceding increases in CO2, you have to ask, what would be the causal mechanism, and how would you explain the preceding temperature rise? There is a well-established chain of causation that goes from increased atmospheric CO2 to temperature rise via radiative forcing, but, other than by positive feedback, whereby a CO2 generated rise in temperature led to – say – drought conditions and vegetation die-back, which resulted in loss of CO2 absorbtion and CO2 release as the vegetation decayed, I cannot see how such a mechanism would work.
I hope that answer your query, Tim. Once again, my apologies for the silly mistake over the Celsius/Fahreheit conversion.

RBlaber has provided so much useful information on this Blog that I hesitate to suggest that he has not really answered Tim’s question about warming preceding the rise in carbon dioxide. As I understand it, historically (speaking geologically) warming from various sources and cycles has indeed preceded greenhouses gases. However this has triggered carbon dioxide and other greenhouse gases which then act as heat traps, and accelerate global warming. These warming cycles take around 5000 years. So typically the natural warming trigger is about 800 years, and the greenhouse gas effect accounts for the other 4200 years. I have to confess that I have cribbed a good deal of this from a scientific site at http://www.realclimate.org/index.php/archives/2004/12/co2-in-ice-cores/
It would seem that our current situation has either been preceded by ‘trigger’ natural warming, and the emissions are now coming into action. Or, as seems more likely, the artificial pumping of emissions from the Industrial Revolution is an altogether new factor making ‘trigger’ natural warming unnecessary.
Incidentally, I have known a number of people who have Asbergers. They seem to me a great gift to the world. They often have a tough time themselves, but the rest of us benefit from the particular talents they often have. As we have seen on this Blog.

Vincent’s contribution is very interesting (and I thank him for his kind words).
I don’t honestly know how to explain (and certainly not how to explain away) the ‘temperature rise preceding greenhouse gas increase’ phenomenon, assuming that Vincent is correct about this. The greenhouse gas increase must certainly result in a _further_ temperature rise, of that there can be no doubt.
It is possible one has to fall back on phenomena such as increases in solar activity or the Milankovic cycle for this, but I am hesitant about doing that.
The increase in greenhouse gases (not just CO2, but CH4, N2O, etc.) since the Industrial Revolution is real, as is the increase in mean annual global temperature since that time.
We would be incredibly foolish to ignore such evidence, and we have to act on the basis that, unless we reduce the amount of greenhouse gas emissions from our economies, we will end up with a temperature rise that leads to unacceptable consequences both for us and for the environment. If there is one case where the precautionary principle is reasonable, then this is it.
We know, for a fact, that previous epochs of warm – or very warm – climate on Earth have been associated with high concentrations of greenhouse gases in the atmosphere. We also know that, if it weren’t for a certain amount of CO2 and water vapour in the atmosphere the surface temperature would be below freezing. We also know of a planet where there is a very large amount of CO2 in the atmosphere, and a runaway greenhouse effect, so much so that the surface temperature is that of molten lead – namely, Venus.
We also know precisely why CO2 and other greenhouse gases produce the greenhouse effect, through their differential absorbtion and reflection of solar radiation. A simple explanation of this can be found at http://www.sciencemuseum.org.uk/energy/site/EIZInfogr9.asp. A more detailed explanation can be found at http://www.ucar.edu/learn/1_3_1.htm.
We have known about the greenhouse effect since the early 1800s, so it is not a new discovery – it is not new science. What is relatively new (from the 1950s onwards) is the concern over the effect of the increasing amount of greenhouse gases going into the air as a result of industrial activity and the effect that that would have on the climate.
We have only got one planet to live on. If we destroy it, then we destroy ourselves in the process. If we do nothing about global warming, we may end up precipitating an ecological catastrophe, and precipitate the much-talked of ‘Sixth Extinction’, with us among the species rendered extinct.
The more frequently I post to this ‘Blog about this subject, though, the more I end up feeling like Cassandra.

Being relatively new to Second Sight, I was beginning to suspect that RMBlaber was actually a team of people – a philosopher, linguist, geneticist, physicist etc. I’m not sure the evidence doesn’t still point in that direction.

One of the big questions in the climate change crisis is how the developed countries can find common ground with the developing countries. In the end everyone loses if things don’t change, but how can we deny the poorer countries of the world the means to grow and develop – which seems to mean industrialise – from our position of wealth and prosperity? As well as reducing our impact we need to provide the means for them to grow their economies in climate friendly ways. Yet the political and economic obstacles to this are surely insurmountable? In the meantime, we can avoid a sense of hopelessness by reducing our own levels of consumption and energy waste, which is not hard to do.

I am a great admirer of RMBlaber’s remarkable erudition and always enjoy his posts. He has no need to apologise for a simple slip. If anything, it is I who should excuse myself for seizing on a small error that does not fundamentally affect the argument.

All that might legitimately be said is that it is too easy for us non-experts to err in drawing conclusions from the findings of the scientists. I would extend that – the scientists themselves can err in deducing what needs to be done. That (to repeat yet again) is not solely a matter of science. Ethics, economics and politics come into it. Ethics sets our goals: one of which is that we have a duty to hand on to our descendants a reasonably liveable world. Politics determine what is practical, and economics what makes economic sense, in seeking to achieve those goals. If we take the purely scientific conclusions as given (which, broadly, I think we must) there is still scope for wide differences of view about ethics, economics and politics.

For example, two important ethical principle are equality and justice. Most people will accept these principles in some form. In climate change discussions, they have two immediate applications: the duty of the developed world, who have been the major producers of CO2 to date, to bear the major cost of dealing with it; and intergenerational equity – we are not entitled to impose unreasonable burdens on generations to come. But it is not so clear what follows. It may be that global warming cannot be prevented without the developed nations sacrificing the economic growth that would bring them nearer First World standards. If so, which is more important? We are not talking about TVs and DVDs for the Third World, we are talking about health, sufficient food and clean water. And on intergenerational equity: our descendants (all over the world) will be markedly better off than us. Assuming (which may be challenged) that they will therefore be better placed to deal with the effects of GW (which by then will be real rather than hypothetical) would not intergenerational equity suggest that they should pay for them, not us? We must help the developing world, but spending enormous sums on mitigating global warming may (according to some economists at least) be a very inferior way of doing it.

Iona, this is based on the IPCC scenarios, all of which suppose substantial economic growth. By 2100 “In the industrialised world, people will see their incomes grow six-fold … Income in the developing countries is expected to soar 12-fold”. (Lomborg, “Cool It”, p 55). That’s using present-day values (ie, stripping out inflation). This may be checked against the IPCC documents, if you think Lomborg has got it wrong.

If we fight global warming by setting stringent CO2 targets, this will curb economic growth to such an extent that we’ll be less able to afford measures to adapt to it (such as flood defences). Thus damage to the environment might be increased rather than reduced. That, at least, is the argument.

Generally (for me at least) global warming is not bad in itself. What is bad is its effects (particularly on global poverty). We should seek the most effective ways of combatting these effects – which may not be CO2 reduction.

But will there be anything to buy with this increased income, if rising sea levels have reduced the amount of land available to us, and unpredictable weather patterns have disrupted the growth of crops?

That depends. If sea levels rise by 70 feet, as James Hansen fears, then there will be problems. If they rise by 50 cm or so, which is about what the IPCC expects, we can spend this increased income on flood defences and have a lot left over for improving health and nutrition. Similarly with the food supply. The most pessimistic IPCC forecast is for a marginal reduction due to climate change – less than the current average annual growth in productivity. The most optimistic forecast is for a net increase.

Of course, things might turn out worse. Shouldn’t we (by cutting emissions) insure against things going wrong? That depends on the cost of the insurance, the cost of disaster, how likely it is – and who pays. I don’t see this as an easy call either way, but incline to the view that the burden of proof is on those who want to spend large sums now to remedy evils that (despite what the development charities’ ads say) haven’t happened yet.

In the UK, and particularly here in Scotland, we are very well placed to observe the effects of Climate Change. If you live in Siberia where the temperature is -40deg throughout the winter you are unlikely to notice that it is a balmy -36deg. Similarly there is little practical difference between a tropical 42deg and 46deg. However if the average temperature is -2C (as it is historically on the summits of Scottish mountains) for 3 months of the year and it changes to +2C you are absolutely going to notice the difference. For one thing, animals which have adapted to turn white for camoflage against snow from late October to early May become highly visible against a dark background and are easily spotted and caught by foxes. These include hares and ptarmigan (a subarctic grouse). Also the famous British “wrong type of snow” becomes much more common. That is snow that turns to slush and then refreezes into rutted ice due the melt-freeze cycle characteristic of the British winter. These are minor effects though. Much worse effects can be expected.